Ask anyone working in weight management what changed over the past five years and you will hear the same answer: hormones. Semaglutide and tirzepatide pulled obesity care away from calorie arithmetic and toward the biology that actually drives hunger, fullness, insulin response, and how much energy the body burns.
That shift is still in motion. Drug development has moved past single-hormone therapy into combinations, medications built to copy several metabolic signals at once instead of one.
You may have run into the term “GLP-5” in forums, videos, or ads. Worth being direct about this. There is no GLP-5 hormone, no GLP-5 receptor, and no FDA-approved medication by that name. What is real is the push toward multi-receptor agonists that combine GLP-1, GIP, glucagon, and amylin. The next step is not a bigger number. It is more signals working together.
Start with the basics: what GLP-1 actually does
GLP-1, or glucagon-like peptide-1, is a hormone the intestine releases after you eat. Three of its jobs matter here.
Appetite
GLP-1 talks to the parts of the brain that handle hunger and reward. Activating its receptor tends to quiet cravings and stretch out the feeling of being full.
Gastric emptying
It slows how fast food leaves the stomach. Fullness lasts longer, and glucose does not spike as sharply after a meal.
Blood sugar
It prompts insulin release when glucose is high and holds back glucagon when glucagon is not needed.
The first wave of hormone-based obesity medications copied this one pathway. Semaglutide, sold as Wegovy for obesity and Ozempic for diabetes, and liraglutide, sold as Saxenda and Victoza, are the familiar names.
Mayo Clinic lists GLP-1 medications among the FDA-approved options for treating obesity, used alongside nutrition, physical activity, and behavioral support rather than in place of them.
Adding GIP: the dual agonists
The next advance paired GLP-1 activity with a second hormone the body already makes, GIP, or glucose-dependent insulinotropic polypeptide. GIP is another incretin released after meals. It helps regulate insulin secretion and appears to influence how fat tissue behaves.
Tirzepatide is the best-known example. It activates both the GLP-1 receptor and the GIP receptor, and the thinking is that the two hormones cover different ground.
What GLP-1 brings
Lower appetite, less food eaten, slower gastric emptying, steadier glucose control.
What GIP brings
Better insulin sensitivity, added metabolic regulation, and effects on fat tissue biology that GLP-1 alone does not produce.
The logic is simple enough. If one hormone governed body weight, single-pathway drugs would work about equally well for everyone. They do not, and that gap is what pushed researchers toward two targets instead of one.
Three receptors at once: retatrutide
Retatrutide is the investigational drug getting the most attention right now. It is built to hit three receptors: GLP-1, GIP, and glucagon. People often call it a triple agonist.
Glucagon is the interesting addition, because it plays a different role than the other two. Where GLP-1 and GIP mostly handle appetite and insulin, glucagon can raise energy expenditure, promote the breakdown of fat, and change how the liver handles metabolism. The goal stops being “eat less” and starts being “burn more.”
A Phase 2 trial published in the New England Journal of Medicine followed adults with obesity on retatrutide for 48 weeks. It reported substantial reductions in body weight, and it identified gastrointestinal effects as among the most common adverse events.
Trials are ongoing. What keeps the industry invested in this approach is the underlying premise: obesity behaves like a complex metabolic condition, not a failure of discipline, and complex conditions rarely respond to a single lever.
Where amylin fits in
Amylin may be the most interesting of the emerging pathways, partly because it comes from somewhere else entirely. It is not an intestinal hormone. The pancreatic beta cells make it and release it right alongside insulin after a meal.
Signals fullness
Amylin tells the brain that enough food has come in. It works on the pathways involved in ending a meal.
Slows the stomach
Like GLP-1, it slows gastric emptying, which controls how quickly nutrients reach the bloodstream.
Holds glucagon down
It limits excess glucose production by the liver after eating.
Notice the overlap with GLP-1 and, more importantly, the difference. Amylin reaches appetite through a separate biological route. That is exactly why researchers are looking at it as a partner to GLP-1 rather than a replacement for it.
Cagrilintide and CagriSema
Cagrilintide is a long-acting amylin analogue and the leading candidate in this category. It is being studied on its own and paired with semaglutide, a combination known as CagriSema.
Semaglutide supplies GLP-1 receptor activation, appetite reduction, and glucose regulation. Cagrilintide adds amylin receptor activation and a second stream of satiety signaling.
A large clinical trial published in the New England Journal of Medicine tested cagrilintide plus semaglutide in adults with overweight or obesity. The combination produced significant weight reduction compared with placebo, and gastrointestinal effects were among the commonly reported adverse events.
This changes how drug development is approached. Instead of hunting for one dominant hormone, the effort now goes into rebuilding the body’s own hormonal balance.
What a multi-hormone medication might cover
Line up the pathways under investigation and the design intent becomes clear. Each hormone handles a different piece of the metabolic picture.
| Hormone pathway | Primary role |
|---|---|
| GLP-1 | Appetite reduction and insulin response |
| GIP | Insulin sensitivity and broader metabolic effects |
| Glucagon | Energy expenditure and fat metabolism |
| Amylin | Satiety and meal regulation |
Combination therapy is hardly a new idea in medicine. Oncology, HIV care, and cardiovascular treatment all rely on drugs that come at a problem from different directions at the same time. Obesity research is arriving at the same conclusion: several biological drivers usually call for several targeted answers.
Why researchers are not stopping at GLP-1
GLP-1 medications changed what is possible in obesity treatment. They also left four open problems that the next generation is trying to solve.
Response varies widely
Some patients lose a great deal of weight on GLP-1 therapy while others see modest results. Mayo Clinic researchers have looked at whether biological differences between patients can predict who responds best, which points toward more personalized obesity care.
Keeping the weight off
Maintaining weight loss after stopping medication remains one of the hardest problems in the field. Future therapies aim at longer-term metabolic regulation, not just the loss phase.
Protecting lean mass
Weight loss takes fat and lean tissue with it. Researchers want to shift body composition, not just move the number on the scale.
Getting off injections
Effective oral versions of these therapies are a major industry goal, and would remove one of the biggest barriers for patients.
Safety, and the questions still open
Promising trial results do not remove the need for medical supervision. These are prescription medications with real considerations attached:
- Gastrointestinal side effects, which are common across this whole drug class
- Choosing the right patient for the right therapy
- Long-term safety data, which is still accumulating for the newer agents
- Cardiovascular outcomes
- What happens after a patient stops treatment
A medication that produces weight loss is not automatically the right medication for a given person. Obesity is a chronic metabolic condition, and the decision has to account for medical history, risk factors, other prescriptions, and what the patient is actually trying to achieve.
So is GLP-5 the future?
Not under that name. There is no GLP-5 receptor and no GLP-5 drug category, and any product marketed that way deserves a closer look before you spend money on it.
The instinct behind the term is not wrong, though. Something is coming after GLP-1, and it looks like multi-pathway metabolic medicine. The combinations already in development or in trials include GLP-1 with GIP, GLP-1 with amylin, GLP-1 with GIP and glucagon together, and other pairings still in early work.
The question driving the field used to be how to suppress appetite. Now it is how to regulate the whole metabolic system accurately. That is the biggest change obesity medicine has seen in decades, and it is happening without a single new number attached to it.
References and public scientific sources
Mayo Clinic. Obesity: Diagnosis and Treatment. mayoclinic.org
Jastreboff AM, et al. Triple Hormone-Receptor Agonist Retatrutide for Obesity, A Phase 2 Trial. New England Journal of Medicine. 2023;389:514-526.
Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 2025.
Mayo Clinic News Network. Study identifies patients with obesity most likely to benefit from GLP-1-based treatment.
U.S. Food and Drug Administration. Prescription medications approved for chronic weight management. fda.gov
National Institutes of Health. ClinicalTrials.gov database for obesity and metabolic drug development. clinicaltrials.gov
American Diabetes Association. Standards of Care in Diabetes. diabetesjournals.org
This page is provided for general educational purposes and is not medical advice. Retatrutide and cagrilintide are investigational and are not FDA-approved for weight management. Individual results vary, and any decision about weight-loss medication should be made with a licensed provider who has reviewed your medical history.
